A couple of days ago I was making a three gallon beer. Based on the beer lore I'd always heard that you don't have to be precise with whirlfloc measurement, I just chucked a tablet in. It fizzed as always, dispersed and I finished my boil. I was very surprised to find that my wort's pH had RISEN in the boil (not supposed to happen that way). Searching my mind and notes for reasons that it may have happened, I came back to whirlfloc. Yes, it's refined carageenan but it also contains baking soda to disperse it, hence the "fizz". A tablet weighs about 2.4 grams, so I was adding a lot of alkali back to my acidic wort, resulting in a higher pH after the boil than before.
So being the science and engineering-minded guy I am, I did the math. I weighed 10 Whirlfloc tabs to get an average of 2.4 g/tab, most sites recommend a tab for 10-15 gallons of wort, so I used 10, or 0.24g Whirlfloc/gallon (divide by 3.875 to get grams/liter). Then I checked the BSG site for Whirlfloc T: They recommend 2 tablets per barrel, 31 US gallons. Using that math, I came out with a safe figure of 0.2 g/gallon.
Why is this important? Beer pH is an important determinant of its flavor. Yes, the yeast will lower the pH but I've always read that the pH going into the fermentor should be between 5.0 and 5.3. The overdose of Whirlfloc got me to about 5.6. So in the future, I'll be crushing the Whirlfloc tab, measuring by weight what I need to add and using that amount to minimize the pH increase.
Hope this is useful to you!
